Position statement - Benefits of health diet and physical activity for cancer survivors

There is evidence that weight management and physical activity may improve the quality of life of cancer survivors, reduce the risk of cancer recurrence, and extend and increase cancer survival.

Key messages

In Australia there are 774,700 people, or about 3.6% of the total population, who have previously been diagnosed with cancer. Cancer survivors may be at increased risk of other health problems, including heart disease, type 2 diabetes and functional impairment, which could be alleviated through lifestyle interventions.

On the basis of the available evidence, Cancer Council Australia supports the adoption of a long-term healthy lifestyle following cancer treatment, to improve quality of life and reduce the risk of cancer recurrence.

Eat more vegetables and fruit – aim for two serves of fruit and five serves of vegetables a day;

Limit alcohol – no more than two standard drinks a day; and

Handle and prepare food safely.

Most of these recommendations are consistent with evidence-based advice on reducing the risk of cancer and with national dietary recommendations to promote general health. They should be considered in the context of cancer survivors' individual health and social circumstances.

Lifestyle interventions for cancer survivors are showing the potential to improve their health and well-being, in particular women with breast cancer. Further research is required to determine the efficacy and effectiveness of specific lifestyle interventions designed for breast cancer survivors and survivors of other cancers.

Background

The role of lifestyle factors in improving survival rates for people with cancer is an emerging area of research.

The American Cancer Society expert panel on nutrition, physical activity, and cancer survivorship has compiled guidelines for cancer survivors regarding body weight, nutrition and physical activity, based on current evidence[1]. The guidelines outline the evidence that physical activity, maintaining a health body weight, healthy eating and food safety have a positive impact for the survivors of certain cancers, with reference to quality of live, recurrence and overall mortality[1].

Recent results from the Women's Intervention Nutrition Study (WINS) and the Nurses Health Study have strengthened the evidence that lifestyle factors can benefit not only the quality of life of cancer survivors, but also overall survival, and decrease the risk of recurrence from breast cancer[2][3][4].

The purpose of this position statement is to outline the evidence for the benefits for nutrition and physical activity interventions for cancer survivors, and provide a rationale for Cancer Council Australia's recommendations for cancer survivors.

Defining a cancer survivor

For the purposes of this position statement, a cancer survivor is defined as someone who has completed their active treatment phase and who is not undergoing palliative care. The nutritional and physical activity needs of most people with cancer change during different phases of treatment and post-treatment recovery. An individual survivor's overall health and social circumstances should be considered before making any lifestyle changes.

Cancer survival in Australia

Estimating the number of cancer survivors in Australia is difficult.There are an estimated 774,700 people in Australia, or about 3.6% of the total population, who have previously been diagnosed with cancer[5]. This number includes people currently living with cancer, estimated at 326,600 people in 2011-12[6].

The number of cancer survivors in Australia is likely to increase due to an ageing population and increasing survival rates for people diagnosed with many cancer types[5].

Cancer survivors may be at increased risk of weight gain, functional impairment, fatigue, other chronic diseases (osteoporosis, cardiovascular disease, type 2 diabetes), secondary cancers and death from non-cancer causes, all of which could be reduced by healthy lifestyle interventions.

The majority of adult cancer survivors do not meet established guidelines for physical activity, diet and weight control, and follow similar behaviours to the rest of the population[7].

Overweight and obesity

Being overweight or obese has been associated with recurrence of breast cancer[8], bowel cancer[9][10], prostate cancer[11] and an increased risk of cancer death[12]. Due to the focus of research to date, most of the existing evidence-based literature on the relationship between healthy body weight and cancer survival outcomes is centred on breast cancer survivors.

Increased body mass index or body weight has been found to be a significant risk factor for decreased survival after a breast cancer diagnosis and for breast cancer recurrence[8][13]. Studies have shown the risk of death from breast cancer after diagnosis increases by 30-54% in heavier women compared with women in the healthy weight range[8][13].

Results from the Nurses Health Study showed that large weight gains after breast cancer diagnosis were associated with a 64% higher risk of recurrence, compared with those women who maintained their weight[2]. Smaller weight gains were associated with smaller increases in risk[2].

A randomised controlled trial known as WINS, involving 2,400 women (aged 48-79 years) with early stage breast cancer[4]. The intervention group received group nutrition counselling to decrease their fat intake. After five years of follow-up, the average fat intake of the control group was 51 g fat and 33 g for the intervention group (~20% energy)[4]. The risk of recurrence was decreased by 24% in the intervention group, compared with the control group[4]. Further analysis is required to determine if it was the decrease in fat intake, the change in fatty acid profile, increase in fibre intake or weight loss that was responsible for the benefits.

The Womens Healthy Eating and Living (WHEL) study, a randomised controlled trial of over 3000 women, evaluated the effect of a reduced-fat diet and increased intake of fruits and high-fibre vegetables among both pre- and postmenopausal women with early-stage breast cancer[14]. The intervention in the WHEL study was delivered by telephone, whereas the WINS intervention was delivered by group counselling.

Physical activity

The benefits of exercise/physical activity for cancer survivors are becoming more apparent, especially in alleviating fatigue[15][16][17][18]. Proven benefits of exercise for cancer survivors include improved cardiovascular fitness, muscle strength, body composition and self-esteem, and reduced fatigue, anxiety and depression[16][18][19]. Such benefits result in overall improvements in several components of quality of life (e.g. physical, functional and emotional).

Physical activity is associated with improved breast cancer survival and reduced risk of recurrence[21]. One of the first studies to show that physical activity improved breast cancer survival rate and not just quality of life was published in 2005[3]. Results from the Nurses Health Study showed that the greatest survival benefit occurred in women who performed moderate activity, such as the equivalent of walking three to five hours per week at an average pace, compared with those women who were sedentary[3]. There was a 26-40% improvement in survival outcomes for those women who were more active compared to the least active women[3].

Recent meta-analysis has suggested that physical activity after diagnosis reduces bowel cancer mortality by up to 35%[22].

It is not currently known what exercise prescription would be most beneficial for which types of cancer, at which stage of disease or treatment. Information is required on the best type, frequency, duration and intensity of exercise to recommend to cancer survivors[23].

Nutrition

There are a small number of studies indicating that diet may play a role in preventing cancer progression and recurrence in people who already have cancer, however intervention studies with cancer end-points are few in number and further research is needed before definitive dietary advice can be given to cancer patients[24]. Evidence that dietary intake of vegetables, fruit or related nutrients (e.g. beta-carotene, vitamin C) reduces cancer recurrence or extends survival is supportive but not conclusive[8]. The effect on risk is likely to be modest.

The WHEL study, a randomised controlled trial evaluating the effect of an increased intake of fruit, vegetables and fibre among both pre- and postmenopausal women with early-stage breast cancer, did not find a statistically significant protective association between those who increased their fruit and vegetable consumption and those who did not[14]. After an average of follow up period of 7.3 years, there were no differences in the risk of recurrence of breast cancer (p=0.63) or in the risk of overall mortality (p=0.43) between the two groups. The women in both groups of the WHEL study experienced small weight gains, so it may be possible that preventing further weight gain may have more of an impact on breast cancer recurrence and survival than just boosting fruit and vegetable intake.

Epidemiological studies suggest that a diet high in vegetables may improve prognosis after the diagnosis of breast cancer[8]. A 43% reduction in overall mortality was observed in a study of breast cancer survivors in association with a dietary pattern characterised by the high intake of vegetables and whole grains[25].

For oral cancers, consuming vegetables, citrus fruit and orange juice has been associated with a better prognosis[26]. In patients with bowel cancer, one observational study of over 1000 survivors found that a diet characterised by a higher intake of red meat, processed meat, refined grains, and sugary desserts was associated with a statistically significant increase in cancer recurrence and poorer overall survival[27].

In a study of prostate cancer survivors, a higher saturated fat intake predicted shorter disease-specific survival and in another, greater monounsaturated fat intake predicted longer survival. Given that men with prostate cancer are at a significant risk of death due to cardiovascular disease, these heart-healthy recommendations appear prudent not only for cancer prevention but also for competing causes of death[28][29].

Fruit and vegetables are recommended for their important role as a low-energy density source of nutrients (vitamins, minerals, phytochemicals and fibre) and their contribution to weight management as well as for their probable cancer protective effect.

The American Cancer Society has issued advice to cancer survivors, particularly of breast, lung, and colorectal cancers, to adopt the general cancer preventative recommendations for fruit and vegetables consumption, although they acknowledge there are few studies that have examined whether this improves cancer survival[1]. WCRF also recommends cancer survivors follow the recommendations for diet and cancer prevention[30].

Alcohol

No studies have found a significant association between alcohol intake and cancer survival, despite the convincing evidence for alcohol being a risk factor for some types of cancer[1][8]. See the Alcohol chapter of the National Cancer Prevention Policy for more information on the link between alcohol and cancer.

Diet supplements

Although diet supplement use is very common among cancer survivors, studies have suggested that supplements are unlikely to improve prognosis or overall survival after the diagnosis of cancer, and may actually increase mortality[31][24].

Foods like vegetables and fruits are complex and contain many different types of nutrients and phytochemicals, which cannot always be replicated in a supplement form. Clinical trials into vitamin supplementation (e.g. beta-carotene) to prevent cancer in particular high-risk groups have not produced evidence in support of their use[32].

It is still prudent to encourage cancer survivors to obtain the potentially beneficial compounds from food. Nutritional supplements are rarely a replacement for a diet rich in vegetables and fruit and their complex mixture of phytochemicals. A daily multivitamin supplement in amounts equivalent to 100% of the recommended dietary intakes is a good choice for cancer survivors who are unable to eat a healthy diet. The use of vitamin and mineral supplements in higher doses should be assessed and discussed on an individual basis. High doses of dietary supplements may be associated with toxicity.

Food safety

Cancer patients undergoing active treatment are at risk of food borne illness, particularly if they are undergoing immunosuppressive treatment. Cancer survivors may be at increased risk of immunosuppression compared to the general population, and therefore should be careful to avoid foods that may contain unsafe levels of pathogenic micro-organisms.

Further research

The link between healthy lifestyle and cancer survival is an emerging scientific concern, but remains understudied in Australia. As people with cancer are at high risk of other chronic diseases, lifestyle interventions are likely to have significant benefits beyond cancer control. Further randomised control trials are required to assess the efficacy of dietary and/or physical activity interventions and advice for cancer survivors. A better understanding of the enabling factors and barriers to cancer patients following dietary and physical activity advice is also required.

Recommendations

Eat more vegetables and fruit – aim for two serves of fruit and five serves of vegetables a day;

Limit alcohol – no more than two standard drinks a day; and

Handle and prepare food safely.

Most of these recommendations are consistent with evidence-based advice on reducing the risk of cancer and with national dietary recommendations to promote general health. They should be considered in the context of a cancer survivor's individual health and social circumstances.